1. Field of the Invention
The present invention relates to integrated circuit devices. More specifically, the present invention relates to a method and an apparatus for detecting position using beams of light between semiconductor dies.
2. Related Art
Advances in semiconductor technology presently make it possible to integrate large-scale systems, including tens of millions of transistors, into a single semiconductor chip. Integrating such large-scale systems onto a single semiconductor chip increases the speed at which such systems can operate, because signals between system components do not have to cross chip boundaries, and are not subject to lengthy chip-to-chip propagation delays. Moreover, integrating large-scale systems onto a single semiconductor chip significantly reduces production costs, because fewer semiconductor chips are required to perform a given computational task.
Unfortunately, these advances in semiconductor technology have not been matched by corresponding advances inter-chip communication technology. Semiconductor chips are typically integrated onto a printed circuit board that contains multiple layers of signal lines for inter-chip communication. However, signal lines on a semiconductor chip are about 100 times more densely packed than signal lines on a printed circuit board. Consequently, only a tiny fraction of the signal lines on a semiconductor chip can be routed across the printed circuit board to other chips. This problem has created a bottleneck that continues to grow as semiconductor integration densities continue to increase.
Researchers have begun to investigate alternative techniques for communicating between semiconductor chips. Proximity Communication is one such alternative technique that communicates using the coupling capacitances between face-to-face chips. The Proximity Communication technique requires good mechanical alignment between chips, and hence requires a method to measure the position between chips. One promising technique involves using light energy to convey position between semiconductor chips. However, it is not a simple matter to build a photo-detector on a semiconductor die with sufficient sensitivity to detect the position of an incident beam of light.
Hence, what is needed is a method and an apparatus for building a photo-detector on a semiconductor die with sufficient sensitivity to detect the position of an incident beam of light.